How to Unlock and Format an External Hard Drive for Your Mac
No matter your operating system of choice, external hard drives can be useful in many situations. Whether you need to move a few files to another system or do a quick backup, it can never hurt to have a few of them around. But an external hard drive for your Mac is only convenient when you can use it.
If you’re facing permission-related issues or can’t add files because the hard drive is locked, then the whole use of a hard drive is defeated. This isn’t often a major problem, and more often than not, it’s simple to solve.
What Does It Mean When a Hard Drive Is Locked on Your Mac?
The concept of unlocking an external hard drive on a Mac may not be familiar to you. This is partially because it can refer to a few different problems:
- The drive is set to read-only permissions, so you can’t add or delete files.
- The external hard drive uses a partially supported file system, like NTFS, which macOS only supports as read-only.
- The drive is encrypted, meaning you can’t access it in any way until you’ve decrypted the disk.
How to Unlock a Hard Drive on macOS
Now you know the probable reasons for the locked drive, let’s explore the steps you can take to fix each of these problems.
1. Fix Permission-Related Issues
Control-click the external drive icon in Finder, then select Get Info. In the Sharing and Permissions section, click the Lock button in the bottom-right corner and type in your username and password.
Then, check the option to Ignore ownership on this volume. By doing this, your Mac treats all the files on the disk as though they’re owned by the current user, no matter who actually owns them. If you’d like to share an external hard drive with other Mac users, this option allows you to seamlessly copy files to and from the drive.
You won’t see this option if the external storage is used as a boot drive or a Time Machine backup drive.
If this is a drive you formatted yourself, you can change the individual permissions in the box above. This lets you set the permissions to Read & Write to yourself while keeping the read-only for other users. Here’s a guide to macOS disk permissions to help you understand the technical concepts.
2. Fix Read-Only External Hard Drive Issue
Is your external hard drive showing up as “read only” on your Mac? This usually happens because the drive is formatted with Microsoft’s NTFS file format. On macOS, you can only read disks in this format, not write to them. As a consequence, you won’t be able to add, change, or delete files.
You can use a third-party app to write to an NTFS disk on a Mac. Or, if you bought an external hard drive from Seagate, it should come with Paragon Driver to let you read and write data interchangeably on Windows and Mac without formatting the drive. There are two separate versions listed on the Seagate site, one for macOS 10.10 to 10.15, and another for the Macs running an Apple silicon chip.
For other drives, they’ll most likely use exFAT, which has no realistic file or partition size limits, or they’ll require complicated ACLs and file attribution system like NTFS. In the event of a crash, though, you might lose data.
Mac computers with Apple silicon chips must change the startup disk security settings to “Reduced Security” for this software to function properly. To do this, start your Mac in macOS Recovery. Then choose Utilities > Startup Security Utility and change the security policy.
3. Decrypt the External Hard Drive
To unlock an encrypted hard drive, Control-click the drive icon in the main Finder. In the menu that pops up, select Decrypt “Drive Name” and enter the password for that drive. This only works if you know the password. And if you don’t, you can still format the drive, which we’ll detail a little further down.
How to Format an External Hard Drive for Mac
Now that you know how to unlock your external drive, you’re ready to format it for use on your Mac. Before you proceed, be aware that this will erase all the data on the drive. Unless you’re positive that you don’t need any data, you should back it up first.
You should also consider how you’re going to use the drive. Different file systems are better for certain tasks, so you’ll need to select the right file system for your needs. If you’re unsure, take a look at our rundown of the best Mac file systems for external drives.
Open the Disk Utility app. In the sidebar, you’ll see a list of internal and external drives. Choose View > Show All Devices to see the storage devices at the top level, containers, and any volumes in each container. Select the external storage device (not the container or volumes it contains) you want to format.
From the toolbar, click Erase. Type in the disk name, then select your preferred option for both Format and Partition Scheme. By default, the option is set to APFS and GUID Partition Map Scheme. When the reformatting is finished, click Done. At last, click the Eject button next to the volume in the sidebar.
Naming the option Erase makes it obvious that the process deletes your data, but this adds confusion in another way. If you’re looking for how to format an external hard drive for Mac, you may not be looking for an option named “erase.”
How to Lock an External Drive on a Mac
If you’re wondering how to lock an external hard drive on a Mac, it’s roughly similar to unlocking it. To render a drive read-only, Control-click the drive, then select Get Info. Here, uncheck Ignore ownership on this volume at the bottom of the window.
In the Sharing & Permissions section, change Read & Write to Read only for each category you wish to change. This will prevent unwanted users or groups from deleting, adding, or changing files on the drive.
It’s simple to encrypt an external hard drive on Mac. Control-click the drive, then select Encrypt “Drive Name” on the drive. Choose a password, type it again, and leave a password hint. Then click Encrypt Disk and wait for the process to complete.
Factors to Consider When Buying an External Hard Drive
Most of us use external hard drives from time to time. If you only use Mac computers in your home, chances are you’re not going to face any issues. You just have to be careful about Time Machine backup compatibility.
However, if you use a Mac at home and a Windows PC in the office, the best option is either exFAT or Seagate drives. With so many kinds and qualities of storage devices, it’s not easy to pick one right away. Read our guide to understand the factors that you should consider when buying an external hard drive for your Mac.